Spinal cord injury (SCI) is a prevalent human trauma that greatly reduces an affected individual’s quality of life. Natural healing post-SCI results in glial and fibrotic scarring, which are common bodily reactions to central nervous system (CNS) injury, but components within these scars unfortunately inhibit axonal regeneration and the sprouting of injured neurons. Interestingly, mammals of the genus Acomys have evolved mechanisms to overcome these deficits and regenerate CNS cells to full functionality post-SCI. Since adult mammalian neurons do have an intrinsic capacity to regenerate, we reasoned that neuron-extrinsic factors are the likely culprit for failed cell regeneration in SCI patients. Thus, the overall aim of our project is to characterize neuron-extrinsic factors such as immune cells and alterations in extracellular matrix (ECM) molecules that give the species Acomys cahirinus their regenerative capacity. We hypothesized that Acomys will exhibit greater axonal regeneration and less fibrotic scarring than the common mouse model, Mus musculus, after SCI. To study this, we produced a clinically relevant contusion SCI in both Mus and Acomys. We then examined major inflammatory cells known to be activated post-SCI. Standard immunohistochemistry targeting IBA1 (a microglia marker) and GFAP (an astrocyte marker) was used to detect: 1) microglia, the first-responders to injury in the CNS and 2) astrocytes, a major component of the glial scar. My analysis showed that more microglia, but less astrocytes, were activated in Acomys than Mus. This suggested that after SCI, Acomys activated less astrocytes but recruited more reparative immune cells compared to Mus. Next, we will examine the distribution of fibroblasts and collagen, important ECM components that compose fibrotic scars, in post-SCI Acomys and Mus tissue. Understanding how neuron-extrinsic factors respond to SCI in Acomys will help us further identify and define cellular targets for the development of novel therapeutics to treat human SCI.

 Alzheimer’s Disease (AD) has well-known brain alterations such as Tau protein build-up, beta-amyloid plaques, and neuronal cell death, yet the role of the brain’s microvasculature on the progression of this neurological condition has not been fully uncovered. My research examines changes in the microvasculature density, length, and function during normal aging using a well-established aging model in Brown Norway rats. This study contributes to the pantheon of previous microvascular research and forwards the field toward understanding AD development from another perspective. My hypothesis is that the density and length of these microvasculature are decreased in areas associated with learning and memory (i.e., the hippocampus and parietal cortex) before the development of AD symptoms and worsen as the disease progresses. To test this hypothesis, first in normal aging, 3 experimental groups of Brown Norway rats are employed: (n=6) young rats at 5-6 months, (n=6) middle-aged rats at 15 months, and (n=6) old rats at 20-24 months. Sagittal slices of the right hemisphere were fluorescently marked for their microvasculature, astrocytes, and cellular nuclei. The ImageJ analytical program was used to compartmentalize the areas of the dentate gyrus, CA1, CA2, and CA3 along with the parietal cortex into 900 x 900-pixel boxes for examination. The preliminary results show that the density of microvasculature within the 3 age groups were consistent while the distribution of the vessel lengths had more variability. The two leading postulates are increased tortuosity with increased age and/or rarefaction, where the microvasculature experience shortening with increased age. Further analysis is needed to examine this distribution among the 3 age groups.

Neurogenic bladder is a common condition associated with traumatic spinal cord injuries (SCIs), which results in inhibited detrusor function, bladder-sphincter dyssynergia, and scarring of the bladder walls and muscle. Care for neurogenic bladder is aimed at reducing abnormally high pressures, which left untreated lead to hypertrophy and tissue fibrosis of the bladder wall, as well as upper urinary tract complications. Current treatments target the neurotransmitter release of acetylcholine, utilizing anticholinergic drugs to counter the overactive bladder. However, these drugs can have negative/deleterious side effects, and have broad symptoms influencing unintended targets around the body. Targeted chemodenervation that uses Botulinum toxin (Botox) to interfere with nerve conduction is often reserved as a second line of defense to treat neurogenic bladder. Unfortunately, this late provision concedes irreversible damage to the detrusor muscle. We hypothesize that administering early chemodenervation can prevent the development of neurogenic bladder, improve bladder compliance post SCI, and increase the overall quality of life of SCI affected patients. Using a rat model, the Khaing lab administers a controlled contusion injury to the T8/T9 vertebrae, simulating a spinal cord injury in humans. The recovery of the rats is tracked with behavioral observations, cystometry data collection, and histological stains. My team and I are working to determine the effective therapeutic time post SCI for Botox injections, and the optimal doses for treatment. Our results thus far support that acute chemodenervation with Botox reduces bladder overactivity, and bladder wall thickness.

Hydrogels are soft materials with high water content that are widely used as scaffolds to interface with the central nervous system (CNS). Spinal cord trauma leads to destruction of a highly organized cytoarchitecture that carries information up and down the spinal column. Experimental therapeutic efforts aim to create scaffolds with aligned topography to support anisotropic regeneration. Current methods are typically complex and make it difficult to introduce specific topography into 3D hydrogels. Here we examined a simple and reproducible system that resulted in consistently aligned fibrils within 3D matrices using thermally gelling biomimetic polymers compatible with neuronal cells. A collagen type I (Col)-based hydrogel system was used in combination with other native extracellular matrix proteins: laminin I (LN) and hyaluronic acid (HA). It was found that all three types consistently formed gels at 37°C. Aspiration and ejection were used to produce hydrogels containing aligned fibrils. Scanning electron microscopy (SEM) images confirmed successful alignment in all gel types, and the size of fibers were consistent with reported values for collagen (~250 nm in diameter). We found that embryonic spinal cord neurons survive and produce processes aligned to collagen fibrils after 14 days in vitro. Next, we investigated the functionality of aligned and un-aligned Col hydrogels implanted acutely after a contusion type spinal cord injury to the thoracic spinal cord at T7/T8. Within all implants, we found pan neuronal-positive fibrils and that the aligned hydrogels supported neurite growth along the parallel direction of the implanted hydrogels. Our data indicate that thermally gelling biomimetic polymers can produce aligned matrices by a method of aspiration and ejection. The material composition and process of aligning hydrogels outlined here presents a novel platform for regenerative therapies for the CNS that is compatible with the survival of neuronal cells in vitro and in vivo.